Day view: create new event at specific time when double-clicking on an hour line.

Minor QoL improvement idea: it would be cool if the day view allowed easy creation of an event or ToDo at a given time by double-clicking on the corresponding cell. If an event already exist, double-clicking it would open the create/modify event dialog. Double clicking on the cell of the first row, with day-long events, could even open the same dialog with "all day event" already check.